Observation apparatuses for observing precipitation phenomena among meteorological phenomena have been developed for more accurate observation in the world since Korean rain gauge was invented in 1441 by King Sejong.
Among these apparatuses, a rain gauge, which is a representative apparatus for observing the rain, is divided into various kinds such as a water storage type cylindrical rain gauge, a water storage type self-recording rain gauge, an inverted type rain gauge, a weight type rain gauge, a load cell type rain gauge and the like. Generally, in the case of snow, there is an observation apparatus for the measurement of snow cover. According to observation methods, the observation apparatus is divided into the kinds such as a snow measuring plate using direct measurement with the eye of a person, an infrared-ray snow observation apparatus using an infrared ray method, a video snow observation apparatus using a video camera, an ultrasonic snow observation apparatus using ultrasonic waves, a laser snow observation apparatus using a laser, and the like.
The observation of precipitation phenomena was focused to typically observe the amount or depth of precipitation. However, since a remote sensing apparatus such as radar, a meteorological satellite and the like was developed, the need to accurately observe the size, shape, concentration, falling velocity of precipitation drops, and the intensity and weight of rainfall has arisen for the quantitative forecast of precipitation.
As a representative apparatus devised for observing precipitation drops in the world, a disdrometer using an optical method has been currently developed and used. This disdrometer is an apparatus for measuring the size and falling velocity of precipitation drops, the intensity and visibility of rainfall, the shape of precipitation and the like, and generates the horizontal beam of rays from a laser transmitter and converts it into an electrical signal in a receiver. In spite of this, it is problematic that the disdrometer adopts a two-dimensional laser method, and thus the shape, volume, and density of precipitation drops (i.e. rain, snow), and the water equivalent of precipitation drops are not accurately observed.